P and A setting with exothermic material

ABSTRACT

A method of plugging a hydrocarbon well includes deploying a downhole tool to remove at least a portion of a casing at a section of well to be plugged. Deploying a blocking device downhole to block a bottom of the section of well to be plugged. Deploying a plugging material downhole onto the blocking device to fill an area to be plugged. Deploying an exothermic fluid downhole, wherein activation of the exothermic material liquefies the plugging material. Allowing the plugging material and the exothermic fluid to solidify form a cast-in-place plug that fills the section of well to be plugged.

PRIOR RELATED APPLICATIONS

This application is a non-provisional application which claims benefitunder 35 USC § 119(e) to U.S. Provisional Application Ser. No.62/598,680 filed Dec. 14, 2017, entitled “P&A SETTING WITH EXOTHERMICMATERIAL,” which is incorporated herein in its entirety.

FIELD OF THE INVENTION

The invention relates to methods, systems and devices for plug andabandonment operations to shut down a well or a portion thereof.

BACKGROUND

The decision to plug and abandon a well or field is often based onsimple economics. Once production value drops below operating expenses,it is time to consider abandonment, even if considerable reservesremain. It is also useful to plug and abandon a well to use an existingslot to sidetrack into new payzones. This process is known as “slotrecovery” and is very cost effective compared to drilling a new completewell. Consequently, plug and abandonment (P&A) is an inevitable stage ina lifespan of a well.

In a typical P&A operation, operators remove existing completionhardware, set plugs and squeeze cement into an annulus at specifieddepths across producing and water-bearing zones to act as permanentbarriers to pressure from above and below. Operators remove the wellheadlast. One of the main problems in any cementing procedure iscontamination. Poor mud-removal in areas where the cement is to be setcan give rise to channels through the plug caused by the drilling fluid.To avoid this, a spacer is often pumped before and after the cementslurry to wash the hole and to segregate the drilling fluid and thecement from each other.

Different regulatory bodies have their own requirements for pluggingoperations. Most require that plugs be placed and tested across any openhydrocarbon-bearing formations, across all casing shoes, and acrossfreshwater aquifers. More and more, metal or alloy plugs are used inplace of or in conjunction with cement to meet these requirements.

SUMMARY OF THE INVENTION

The invention relates to methods, systems and devices for plug andabandonment operations to shut down a well or a portion thereof.

One example of the invention includes a method of plugging a hydrocarbonwell, the method including deploying a downhole tool to remove at leasta portion of a casing at a section of well to be plugged; deploying ablocking device downhole to block a bottom of the section of well to beplugged; deploying a plugging material downhole onto the blocking deviceto fill an area to be plugged; deploying an exothermic fluid downhole,wherein activation of the exothermic material liquefies the pluggingmaterial; and allowing the plugging material and the exothermic fluid tosolidify form a cast-in-place plug that fills the section of well to beplugged.

Another example of the invention includes a through-tube method ofplugging a hydrocarbon well, the method including deploying a downholetool downhole to at least partially remove a tubular or a casing, at asection of well to be plugged; deploying a blocking device downhole toblock a bottom of the section of well to be plugged; deploying aplugging material downhole onto the blocking device to fill an area tobe plugged; deploying an exothermic fluid downhole to heat and form aliquefied plugging material; and allowing the liquefied pluggingmaterial to solidify and fill the section of well to be plugged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1H shows one embodiment of the inventive method as described inthe specification.

DETAILED DESCRIPTION

The present disclosure provides systems, methods and devices for a P&Aoperation. The present invention describes ways to remove a short regionof tubing and/or casing and access the plugging interval. The presentinvention may also be useful for non-abandonment plugging applicationssuch as slot recovery, temporary abandonment, and the like. Developedherein is a method of plug and abandonment, which is shown schematicallyin various embodiments in the figures.

As used herein, “tubular” or “tubing” refers generically to any type ofoilfield pipe, such as, but not limited to, drill pipes, drill collars,pup joints, casings, production tubings and pipelines. In some cases,the outer one or more tubing sets may be referred to as “casing” or“casings.”

If a section of a well to be plugged is not cemented or is only poorlycemented, access to the annular space between the tubing and casingand/or between the outermost casing and reservoir is needed so that anabandonment plug can be placed right up the formation for a rock-to-rockplug. This can be accomplished by one or more steps as described herein.

FIG. 1A shows a section of casing 101 to be plugged. This casing 101 issituated in a wellbore. FIG. 1B shows the casing 101 after a perforationand wash step using a perforate and wash tool (PWT). The PWT createsperforations 102 that exposes the annular space between the casing 101and the wellbore. Typically, this annular space either lacks cement orlacks quality cement.

As used herein, a “perforate and wash tool” cuts small holes or slots inthe tubulars and washes or cleans the perforated zone. This allowspermanent rock-to-rock plugging to be possible during a single trip.These are typically used to convert a designated region of casing toproduction use, the plurality of discrete holes allowing ingress of oil.Such tools can also be used herein in the P&A process.

While this embodiment describes a perforation and wash method to accessthe casing annulus, other methods may also be used. These include, butare not limited to, cutting using cutters, section milling, perforatingwithout washing, helical cutting using laser, propellants, and the like.Moreover, while FIGS. 1A-1H show only a single casing, this is notintended to be limiting. The present invention may be compatible withnumerous casing and/or tubing configurations including one or morecasing strings. All the steps of the present invention can be performedthrough-tubing, that is, without having to remove existing tubing.

As used herein, a “cutter” is any downhole tube that can be used to cutcasing and/or tubing. A cutter is often used downhole when a tool isstuck to retrieve the tubing string and send down fishing tools. Thereare several different types of cutters including external cutter,chemical cutter, jet cutter, and the like. An external cutter is a typeof cutter that slips over the fish or tubing to be cut. Special hardenedmetal-cutters on the inside of the tool engage on the external surfacesof the fish. A chemical cutter is usually run on wireline to severtubing at a predetermined point when the tubing string has become stuck.When activated, the chemical cutter forcefully directs high-pressurejets of highly corrosive material in a circumferential pattern againstthe tubular wall. The nearly instantaneous massive corrosion of thesurrounding tubing wall creates a relatively even cut with minimaldistortion of the tubing, aiding subsequent fishing operations.

In some embodiments, the present method is considered a “through-tubing”method since at least a portion of the tubing is left in place for theP&A operation. However, the term “through-tubing” does not mean that notubing may be removed at the section to be plugged. Nevertheless, theterm “through-tubing” will be used because the entirety of the tubingneed not be pulled out of the well prior to the P&A operation.

Typically, in conventional P&A, the tubing is pulled and the well issecured with barriers, plugs, fluid, or other methods and a Christmastree is replaced with a blowout preventer. This blowout preventer willneed to be large (˜13⅝ inches) which in turn requires expensive modularoffshore drilling unit (MODU) offshore well installation.

An advantage of through tubing P&A is that the large blowout preventer(BOP) is not needed because the well can be fully secured by permanentplugs in the wellbore before removing the Christmas tree. As usedherein, a “Christmas tree” refers to an assembly connected to the top ofa well to direct and control drilling and/or production. Because use ofMODU is avoided, cost is kept down significantly. On some installations,two wells can be plugged at the same time provided there is sufficientroom for two or more P&A operations.

In some embodiments, perforation and wash can be performed in separatesteps. Or alternative, the wash step may be optional. Scale, drillingmud, swarf (if present) can be washed using a tool (e.g., jet washer)drawn down on a coil tubing to clean out. It may be desirable to performthis wash later. Due to its relatively high specific gravity, debriswill tend to float out.

Referring to FIG. 1C, a blocking device 104 (e.g., inflatable basket) islowered to a selected depth via a wireline 103. As shown in FIG. 1C, theblocking device 104 is installed near the perforated zone to form thebottom of a cavity. The blocking device 104 provide a base for theabandonment plug (introduced later). A blocking device is any deviceused to place settable materials (e.g., cement, resin, metal alloy,etc.) at the desired depth. The blocking device provides a stable baseon which to set the cast-in-place abandonment plug. Suitable blockingdevices include baskets, inflatable baskets, plugs, packers and thelike. Other suitable blocking devices include cement plugs, bariteplugs, sand plugs, resin plugs, and the like. Since the blocking devicemerely acts as a base for a permanent plug, it does not necessarily haveto permanent as a standalone.

Once the blocking device 104 is installed (FIG. 1D), the wireline 103can be retracted and the well is ready to be plugged. Referring to FIG.1E, a plugging material 105 is introduced into the cavity. In theembodiment shown, the plugging material 105 is introduced as solidpellets that fill up the cavity space. The plugging material 105 can be,for example, a low melt alloy that expands upon solidification. Thealloy can be placed by dropping with a dump bailer or dropping alloypellets or chips from the surface. The cavity is filled with alloypellets to the level desired. If needed, the cavity can be assessed atvarious times by an assessment tool such as a camera or sonic tool.These tools can be used as a downhole probe to determine cavity size andextent of access to the reservoir. This and similar verification stepsmay be useful initially but may be omitted once sufficient experiencehas been gained. If mapped, the cavity volume will be known and anappropriate number of pellets can be dumped. Levels can be confirmed byrunning wireline. The extra amount of alloy allows radial expansion,thus improving the seal.

In some embodiments, a low melt alloy may be combined with additionalcement or resin or geopolymer plug. The combined material is used to seta cast-in-place abandonment plug according to regulations and/or aswellbore dictates. Low melt alloys or fusible alloys have low meltingtemperatures and can expand when solidifying from a liquid to a soliddepending on the product.

Compatible low melt alloys include bismuth alloys that contain tin,bismuth lead, and the like. In general, bismuth alloys of approximately50% bismuth exhibit little change of volume (1%) during solidification.Alloys containing more than this tend to expand during solidificationand those containing less tend to shrink during solidification. Otherbismuth alloy may include bismuth and germanium and/or copper. Bismuthalloys are desirable as cast-in-place abandonment plug material becausethey expand upon going from liquid to solid state (bismuth expands1-3.32% on solidification). This allows the alloys to precisely conformto its surroundings. In a cast-in-place abandonment plug, the expansionmeans that the plug will expand to firmly contact the reservoir walls,as well as any metal casing or tubing, and provide a tight seal. Bismuthalso has very low toxicity for a heavy metal. Unlike cement, theseliquid alloys do not mix with other fluids. Consequently, channelingwhich is common in cement plugs can be avoided or significantly reduced.

The bismuth alloys may be released downhole as solid pellets or otherconvenient shapes. In its liquid form, the bismuth alloy has awater-like viscosity, easily penetrating and conforming toirregularities downhole. Because of the properties described herein,bismuth alloys can typically penetrate deeper into the reservoir ascompared to cement. The bonding should also be tighter yet the finalplug will be ductile. The high quality of the material and its bondallows a shorter length to be plugged, thus even if cutting or millingsteps are performed, the interval is much shorter than typical, greatlysaving time and cost.

In some embodiments, the plugging material may be a suitable metal.These include, for example, aluminum, lead, or other metal with meltingtemperature that can be reached by the exothermic reaction.

Exothermic reactions are typically the result of mixing two differentmaterials. The reaction can be started by, external energy (ignitori.e.), simply mixing the two materials together (resin/hardener;hydrogen peroxide/yeast), material exposed to certain type of fluid, orthe materials reach a certain temperature. The exothermic energygenerated can be calculated for any materials. The peak temperature canbe determined. The temperature over time can be calculated andrelationship of temperature/time developed.

The metal or alloy used should melt at a temperature below thecalculated peak temperature. The exothermic material should remain in aliquid, powder, or pellet state until the metal can melt and flow to theplugging point by gravity segregation. Metal will solidify whentemperature decreases or the metal falls below the point where theexothermic reaction is occurring.

The temperature in the well to be abandoned will also be a factor. Asthe temperature will be higher than ambient (30° C. to 100° C. plus) theheat from exothermic reaction will be lower than what is required on thesurface. The downhole temperature must be considered when consideringthe type of metal and heat generated by the exothermic reaction.

The downhole temperature will determine the heat loss. The exothermicheat generated, energy to change state of the metal, and the heat losscan be calculated and overall thermal relationship developed for thetime period. The relationship can be tested in the laboratory.

Referring to FIG. 1F, an exothermic material 110 is introduced into thecavity. The exothermic material 110 is initially in fluid form that canbe introduced through tubing 111 and/or through the annular space 112between the tubing 111 and casing 101. In some embodiments, theexothermic material 110 may be introduced via a bailer, through drillpipe, and/or ran through coil tubing.

There are several advantages of using an exothermic fluid overconventional methods (e.g., heater on a wireline or drill pipe).Conventional methods restrict the volume of metal that can be run. Whenusing a single heater, approximately 30 feet of metal can be melted.Regulatory requirements typically require that the heater be pulled fromthe plug after heating. By contrast, the present invention does notplace strict restrictions on the alloy volume that can be melted andplaced. The alloy pellets can be easily dropped from the surface to fillthe wellbore. Consequently, the alloy pellets do not have to run withwireline or on a drill pipe as molded assembly.

As shown in FIG. 1G, the exothermic material 110 settles to the bottomof the cavity, filling interstitial space created by the stacking of theplugging material 105. In some embodiments, the exothermic material 110is immiscible with any wellbore fluids present so it does not becomediluted. In some embodiments, the exothermic material 110 may have adensity higher than one or more wellbore fluids. Once activated, theexothermic material 110 will release heat sufficient to melt theplugging material 105. When sufficiently heated, the plugging material105 liquefy and easily flow into voids located in the wellbore and allaround the casing fragments. This precludes the need for a squeeze step.

Suitable exothermic materials include, but are not limited to, epoxies,resins, cement (when setting), water and potassium chloride mixed, andthe like. Activation of the exothermic material will depend on the typeof material used. Amount of heat generated can be controlled by thetype, amount of material(s) used, and the like. The resulting plug willbe a two or more material plug that includes the alloy and theexothermic material. The alloy metal plug will typically expand whensolidifying while the exothermic material can shrink. The simultaneousexpansion of the alloy can offset shrinkage of the exothermic material.

Commercially available exothermic materials can be obtained from, forexample, WEST SYSTEM® (Bay City, Mich., USA). WEST SYSTEM® providesepoxies that have peak exotherm temperatures (4 fluid ounce mixtures)ranging from about 155° C. to about 212° C. The time to reach the peakexotherm temperature can range from about 15 minutes to about 75minutes. Insulating fillers can also be used to change peak temperatureand time to peak temperature as needed.

Referring to FIG. 1H, the plugging material 105 and the exothermicmaterial 110 have solidified to form an abandonment plug 115. A shown,the solidified exothermic material 110 rests on top of the solidifiedplugging material 105. In one or more embodiments, the abandonment plug115 can be further capped with cement or another material to meetregulatory requirements, or as otherwise needed. A cement plug can alsobe set under the cast-in-place abandonment plug. Alternatively, or inaddition to, the abandonment plug can also be combined with a resin plugor a geopolymer plug, or combinations thereof. If needed, quality of theabandonment plug can be assessed by drilling a small hole to allowaccess for logging tools. Once assessment is complete, the small holecan be plugged with alloys, cement/resin, or something similar.

In some embodiments, the abandonment plugs can be pressure tested withinhours (cement can require one or more days to set). Since a truemetal-to-metal and metal-to-wall seals are made (no elastomers used), apermanent gas/liquid tight seal is created. Alloy plugs can be set inundamaged, damaged or even corroded casing. The alloy is inert,environmentally friendly and generally immune to corrosion and hydrogensulfide or acid attacks.

The cast-in-place operation can be repeated as needed to set more alloyor other material until the cavity is filled to the desired level. Ifnecessary, a squeezing step can be applied as well. If the selectedalloy expands sufficiently, squeezing step may be avoided.

If desired or required by regulations, a bore can be made in the plugand a logging tool run to confirm the placement and quality of the plug.A drilling tool can be deployed with, e.g., coiled tubing, to allowlogging or other tool to log the plug and confirm the quality. Thelogging tool can measure several different characteristics including i)radioactivity if safe radioactive material is placed in the plugmaterial; ii) degree of bonding to the formation using a sonic orultrasonic cement bond logging tool; or iii) other types of logging.

Once solid connection between the expanded casing and formation isconfirmed, cement or alloy or other material refills hole over plug andmay optionally provide a small overcap on plug. This is preferably doneby using an alloy plug set in similar way, but cement or other materialcan be placed. Cement can be placed by coil tubing, dump bailed, orother compatible means.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

REFERENCES

All of the references cited herein are expressly incorporated byreference. The discussion of any reference is not an admission that itis prior art to the present invention, especially any reference that mayhave a publication date after the priority date of this application.Incorporated references are listed again here for convenience:

-   1. U.S. Pat. No. 6,474,414, (Gonzalez, et al.) “Plug for tubulars.”-   2. U.S. Pat. No. 6,664,522, (Spencer) “Method and apparatus for    sealing multiple casings for oil and gas wells.”-   3. U.S. Pat. No. 6,828,531, (Spencer) “Oil and gas well alloy    squeezing method and apparatus.”-   4. U.S. Pat. No. 6,923,263, (Eden & Eden) “Well sealing method and    apparatus.”-   5. U.S. Pat. No. 7,152,657, (Bosma, et al.) “In-situ casting of well    equipment.”-   6. U.S. Pat. No. 7,290,609, (Wardlaw, et al.) “Subterranean well    secondary plugging tool for repair of a first plug.”-   7. U.S. Ser. No. 10/113,386, (Carragher), “Apparatus for Use in Well    Abandonment.”-   8. US20060144591, (Gonzalez, et al.) “Method and apparatus for    repair of wells utilizing meltable repair materials and exothermic    reactants as heating agents.”-   9. US20100006289, (Spencer) “Method and apparatus for sealing    abandoned oil and gas wells.”-   10. US20130333890, (Dagenais, et al.) “Methods of removing a    wellbore isolation device using a eutectic composition.”-   11. US20130087335, (Carragher & Richard) “Method and apparatus for    use in well abandonment.”-   12. US20150345248, US20150368542, US20160145962, (Carragher)    “Apparatus for use in well abandonment.”-   13. US20150368542, (Carragher) “Heat sources and alloys for us in    down-hole applications.”-   14. US20150053405, (Bakken) “One trip perforating and washing tool    for plugging and abandoning wells.”-   15. US-2018-0148991 (Hearn, et al), “Tool for Metal Plugging Or    Sealing Of Casing.”-   16. US-2018-0094504 (Hearn, et al), “Nano-thermite Well Plug.”-   17. US-2018-0216437 (Shafer), “Through Tubing P&A With Two-Material    Plugs.”-   18. US-2018-0258735 (Shafer), “Helical Coil Annular Access Plug and    Abandonment.”-   19. US-2018-0298715 (Shafer), “Two-Material P&A Plug.”

The invention claimed is:
 1. A method of plugging a hydrocarbon well,comprising: a) deploying a downhole tool to remove at least a portion ofa casing at a section of well to be plugged; b) deploying a blockingdevice downhole to block a bottom of the section of well to be plugged;c) deploying a plugging material downhole onto the blocking device tofill an area to be plugged; d) deploying an exothermic fluid downhole,wherein activation of the exothermic fluid liquefies the pluggingmaterial; and, e) allowing the plugging material and the exothermicfluid to solidify and form a cast-in-place plug that fills the sectionof well to be plugged.
 2. The method of claim 1, wherein the downholetool is selected from the group consisting of: a cutter, a section mill,perforate tool, perforate and wash tool, laser, and propellant.
 3. Themethod of claim 1, wherein about 1 to 5 meters section of casing is atleast partially removed.
 4. The method of claim 1, wherein the pluggingmaterial is a bismuth alloy, aluminum, or lead.
 5. The method of claim1, wherein the exothermic fluid is selected from the group consistingof: epoxies, resins, hardener, hydrogen peroxide, yeast, cement, andpotassium chloride.
 6. The method of claim 1, wherein the pluggingmaterial has a higher density than the exothermic fluid.
 7. The methodof claim 1, wherein the plugging material is deployed prior to deployingthe exothermic fluid.
 8. The method of claim 1, wherein the blockingdevice is a plug, a packer, or a basket.
 9. The method of claim 1,wherein the plugging material expands upon solidification.